Invention Grant
- Patent Title: High-yield-ratio, high-strength cold-rolled steel sheet and production method therefor
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Application No.: US15128516Application Date: 2015-03-17
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Publication No.: US10253389B2Publication Date: 2019-04-09
- Inventor: Katsutoshi Takashima , Kohei Hasegawa
- Applicant: JFE Steel Corporation
- Applicant Address: JP
- Assignee: JFE Steel Corporation
- Current Assignee: JFE Steel Corporation
- Current Assignee Address: JP
- Agency: DLA Piper LLP (US)
- Priority: JP2014-073268 20140331
- International Application: PCT/JP2015/001455 WO 20150317
- International Announcement: WO2015/151427 WO 20151008
- Main IPC: C21D9/46
- IPC: C21D9/46 ; C21D1/25 ; C21D8/02 ; C21D8/04 ; C22C38/02 ; C22C38/04 ; C22C38/06 ; C22C38/08 ; C22C38/12 ; C22C38/14 ; C22C38/16 ; C22C38/28 ; C22C38/38 ; C22C38/58 ; C22C38/00 ; C23G1/00

Abstract:
A high-yield-ratio, high-strength cold-rolled steel sheet has a composition containing, in terms of % by mass, C: 0.13% to 0.25%, Si: 1.2% to 2.2%, Mn: 2.0% to 3.2%, P: 0.08% or less, S: 0.005% or less, Al: 0.01% to 0.08%, N: 0.008% or less, Ti: 0.055% to 0.130%, and the balance being Fe and unavoidable impurities. The steel sheet has a microstructure that contains 2% to 15% of ferrite having an average crystal grain diameter of 2 μm or less in terms of volume fraction, 5 to 20% of retained austenite having an average crystal grain diameter of 0.3 to 2.0 μm in terms of volume fraction, 10% or less (including 0%) of martensite having an average grain diameter of 2 μm or less in terms of volume fraction, and the balance being bainite and tempered martensite, and the bainite and the tempered martensite having an average crystal grain diameter of 5 μm or less.
Public/Granted literature
- US20170107591A1 HIGH-YIELD-RATIO, HIGH-STRENGTH COLD-ROLLED STEEL SHEET AND PRODUCTION METHOD THEREFOR Public/Granted day:2017-04-20
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